As a sliding part having reduced frictional resistance and improved durability and generating no noise, a sliding part is known that is a flat powder formed by sintering a powder compact, which is fabricated by filling an iron-based raw powder and a copper-based raw powder in a filling portion of a forming mold and applying vibration to the mold at the same time for compacting, and having an aspect ratio of the copper-based raw powder larger than that of the iron-based raw powder, on a surface of which copper segregates (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2003-221606); or a sliding part that is a flat powder formed by sintering a powder compact, which is fabricated by filling the iron-based raw powder and the copper-based raw powder into the filling portion of the forming mold and applying vibration to the mold at the same time for compacting, and having an average value of a maximum projected area of the copper-based raw powder larger than that of the iron-based raw powder, in which the copper-base raw powder contains flat powder of copper or copper-alloy and on a surface of which copper segregates (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2004-84038).
Furthermore, as a sliding part, an Fe-based sintered alloy bearing that contains a composition which includes Cu, C and calcium fluoride, where the remainder consists of Fe and unavoidable impurities, and a basis material that contains pearlite and bainite as main constituents are known. The calcium fluoride is dispersed and distributed in the basis material to improve the seizure resistance property significantly, and miniaturizes Cu, which is dispersed and distributed in the basis material, and inhibits the Cu solid solution in the basis material in order for as much Cu as possible to be dispersed and distributed, and improve the toughness (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2001-303217).
However, in the above related art of Japanese Unexamined Patent Application, First Publication No. 2003-221606 and Japanese Unexamined Patent Application, First Publication No. 2004-84038, the mixture of the iron-based raw powder and the copper-based flat raw powder composed of flat powder having a larger aspect ratio than the iron-based raw powder is filled into the filling portion of the forming mold, and at the same time vibration is applied to the forming mold, such that the copper-based flat raw powder segregates at the outer side within the filling portion, overlaps each other in the thickness direction, and at the same time segregates at a gathering surface in a state in which the direction intersecting the thickness direction is aligned with the longitudinal direction of the surface. However, the iron-based raw powder emerges at a part of the surface, as well as the segregated copper-based flat raw powder, and a gap is formed between the copper-based flat raw powders which emerges at the surface and are adjacent to each other. As a result, the gap between the copper-based raw powder and the iron-based raw powder, or the gap between the copper-based flat raw powders is formed in the surface. Due to these gaps, the surface coverage ratio of the copper in the sliding part cannot be increased.
Furthermore, in the above related arts of Japanese Unexamined Patent Application, First Publication No. 2001-303217, though the sliding part can improve the seizure resistance property, the surface coverage ratio of the copper in the sliding part cannot be increased like the above two related arts.
Accordingly, it is an advantage of the present invention to increase the surface coverage ratio of the copper in the sliding part formed by filling the iron-based raw powder and the copper-based raw powder having an aspect ratio larger than that of the iron-based raw powder into the filling portion of the forming mold, compacting the raw powders to form a powder compact, and sintering the powder compact, in which the copper segregates at the surface of the sliding part.